Endoscope pressure equalization system and method

ABSTRACT

A pressure equalization device connects to a port on an endoscope and equalizes the pressure within the endoscope to an environment thereabout. An outlet check valve allows flow out of the port and blocks flow into the port. A filter may be provided for preventing known chemical agents from entering the port. If the agent is hydrogen peroxide, the filter preferably comprises a catalyst, such as copper wool, for decomposing the hydrogen peroxide into water and oxygen. An inlet check valve may also be provided to communicate with the endoscope port and allow flow into the port in response to a downstream pressure gradient exceeding a predetermined value.

This is a division, of application Ser. No. 08/446,377, filed May 22,1995, Now U.S. Pat. No. 5,634,880 which is hereby incorporated byreference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a system and method for equalizingpressure between an interior space in an endoscope and an environmentabout the endoscope.

2. Background Information

A typical endoscope comprises an elongated tube suitable forintroduction into a human or animal body. A lens at a distal tip of theendoscope forms an image of an internal area of the body. Means such asfiber optic cables or video transmission transmit the image the lengthof the endoscope to a point outside of the body where it can be viewedby a surgeon or other user of the endoscope. Of course, endoscopes arenot limited to medical uses, and are also useful in machine diagnosticsand repair among other uses. Regardless of its intended use, a flexibledistal portion allows the endoscope to negotiate non-linear passages.

In addition to the image transmission means, the distal portion of theendoscope typically contains one or more tubular passages for passingair, liquid, or instruments. Flexible endoscopes usually also containone or more wires for controlling movement of the tip of the endoscope.A flexible sheath surrounds the flexible portion of the endoscope toprotect it from its environment and to protect the body or otherenvironment from the internal parts of the endoscope.

For reasons of sanitation endoscopes are typically washed and sterilizedafter each use. For added convenience during these procedures, manyendoscopes are provided with an entirely water tight structure toprotect the internal components of the endoscope from washing andsterilization agents. In a flexible endoscope, the flexible elastomericsheath surrounding the flexible portion of the endoscope forms anintegral part of this water tight structure.

Traditional methods of sterilization, such as high pressure steam, maydamage the delicate internal workings and the flexible sheath of anendoscope. The latest sterilization equipment subjects the endoscope toan antimicrobial gas such as hydrogen peroxide or ethylene oxide,perhaps in combination with a plasma field. These sterilizers typicallymaintain the endoscope in a reduced pressure environment during thesterilization procedure.

A significant area of unused space occupies the flexible portion of mostendoscopes. Of course, this space is filled with gas, typically air. Asthe pressure is reduced, the gas trapped inside of the endoscope exertstremendous pressure against the elastomeric sheath. If this pressure isnot released, the sheath could rupture. In general rigid endoscopeseasily withstand a one atmosphere pressure exerted by entrapped gases;however, even rigid endoscopes may be constructed with delicatecomponents that are sensitive to pressure within the endoscope.

At least one manufacturer provides an endoscope with a sealable portleading into the interior of the endoscope. During sterilization in areduced pressure environment the port may be opened to allow theinterior of the endoscope to communicate with the sterilizationatmosphere and thus relieve the excess pressure within the endoscope.The port is also used to check for leaks in the endoscope, especially inthe sheath, through the controlled application of gas pressure to theendoscope's interior while it is submerged in water.

For convenience, at least one manufacturer supplies an apertured capwhich may be fitted over the port during sterilization which opens avalve within the port and thus places the interior of the endoscope intocommunication with the atmosphere during the sterilization procedure.While this simple device protects the elastomeric sheath from bursting,it also allows the gaseous antimicrobial agent to enter the interior ofthe endoscope. Presence of this agent within the endoscope is notnecessarily desirable. This portion of the endoscope does not come intocontact with the patient so does not require sterilization. Further, theagent could possibly harm the interior of the endoscope. Generally, theport should be left open for a sufficient amount of time after thesterilization procedure for the agent to disperse from the interior ofthe endoscope. Of course, this may increase the length of time requiredto complete the sterilization procedure.

SUMMARY OF THE INVENTION

The present invention overcomes these and other limitations in the priorart by providing a device and method for equalizing the pressure withinan endoscope during a sterilization procedure while inhibiting theantimicrobial gas from entering the interior of the endoscope.

A pressure equalization device according to the present inventionequalizes the pressure within an endoscope with an environmentthereabout. The device connects to a port on the endoscope which in turnleads to the internal space from the environment. An outlet check valvecommunicates with the endoscope port and allows flow out of the portwhile inhibiting flow into the port. Thus, when the endoscope issubjected to a reduced pressure in the environment, gas within theendoscope interior space escapes to the environment through the outletcheck valve to relieve pressure within the interior space. After thepressure in the interior space is equalized with the pressure in theenvironment, the outlet check valve inhibits reverse flow therethroughof gas from the environment into the interior space.

Preferably, the filter in the outlet flow path prevents hydrogenperoxide from entering the port. Thus, when the device is employedduring a reduced pressure hydrogen peroxide sterilization procedure,hydrogen peroxide which may happen to leak past the outlet check valvetowards the port is filtered by the filter. The filter may comprise acatalyst, such as copper wool, for decomposing hydrogen peroxide towater and oxygen.

Preferably, an inlet check valve means also communicates with theendoscope port to allow flow into the port in response to a downstreampressure gradient exceeding a predetermined value, preferably in therange of 1.5 to 5 pounds per square inch. Positive closure means on theoutlet check valve may be provided to inhibit flow therethrough exceptin response to a downstream pressure gradient exceeding a predeterminedvalue, also preferably 1.5 to 5 pounds per square inch.

The port on such endoscopes often have an internal valve and the deviceof the present invention is preferably provided with an opening meansfor opening the port's internal valve. To enhance operator compliance,the device may be attached to a sterilzation container for containingthe endoscope during a sterilization procedure, the sterilizationcontainer being sealable, gas transmissive and microbe impervious.

The present invention also comprises a method for equalizing thepressure within an interior space of an endoscope with a pressure in anenvironment about the endoscope. The method comprises the followingsteps. When the pressure in the interior space exceeds the pressure inthe environment by more than a predetermined value, open a port betweenthe interior space and the environment to equalize the pressuretherebetween. When the pressure within the interior space is equalizedwith the pressure in the environment, block the port to inhibit flow ofgas or other matter from the environment into the interior space throughthe port.

When the gas in the environment contains a known agent, it is preferablyfiltered as it enters the port from the environment to neutralize theagent. When the agent comprises hydrogen peroxide, it is preferablyneutralized with a catalyst, such as copper, which decomposes thehydrogen peroxide into water and oxygen.

The method is most preferably employed in conjunction with asterilization procedure in which the endoscope is placed into asterilization chamber, the pressure is lowered below atmosphericpressure, an antimicrobial gas is introduced into the sterilizationchamber, the gas is scavenged from the sterilization chamber and thepressure within the sterilization chamber is returned to atmosphericpressure.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of an endoscope of the general type forwhich the device and method according to the present invention areadapted;

FIG. 2 is a perspective view of a pressure port of the endoscope of FIG.1;

FIG. 3 is an elevation view of a device according to the presentinvention;

FIG. 4 is a partial sectional view taken along lines 4--4 of FIG. 3; and

FIG. 5 is a diagrammatical view of the device of FIG. 3 in place upon anendoscope and which is further attached to a sterilization containershown in block diagram form.

DETAILED DESCRIPTION

Referring now to FIG. 1, a typical endoscope 10 comprises a flexibleportion 12 for insertion into a body with the flexible portion beingencased within an elastomeric sheath 14. A port 16 opens to an interiorspace (not shown) of the endoscope 10 and allows pressure communicationbetween the interior space and the environment about the endoscope 10.

Turning to FIG. 2, the port 16 comprises a cylindrical body 18projecting outwardly from the endoscope 10. An annular rotatable collar20 is received within the port body 18 and an annular cover plate 22disposed above the collar 20 rigidly connects to the body 18. Rotationof the collar 20 operates a valve member 23 to selectively open andclose the interior of the endoscope 10 to atmosphere through the port16.

A guide pin 24 projects radially from the port body 18 and a notch 26 onthe cover plate 22 aligns with a notch 28 on the collar 20 so that a pin(not shown in FIG. 2) may travel axially into the collar notch 28 forrotation of the collar 20. The port 16 is adapted to receive at leasttwo devices. The first, a sterilization cap (not shown) has a track forreceiving the guide pin 24 and an engagement pin for engaging the collarnotch 28. When the cap is placed onto the port 16 and rotated, the valvemember 23 opens to place the interior of the endoscope 10 into pressurecommunication with the atmosphere through a hole in the cap. The port 16is also adapted to receive a leakage detector, such as disclosed by theShimizu U.S. Pat. No. 4,506,544, issued Mar. 26, 1985 and incorporatedherein by reference.

FIG. 3 illustrates an improved sterilization cap 30 according to thepresent invention. The cap 30 comprises a generally cylindrical body 32which has a channel 34 therein for receiving the guide pin 24 on theport 16 (see FIG. 2). The channel 34 extends axially into the body 32 ashort distance from a body first end 36 from whence it extends onequarter of the circumference of the body 32. Accordingly, the cap 30 maybe placed over the port 16, with the pin 24 received within the channel34, and the cap 30 then rotated one quarter turn as the guide pin 24travels along the channel 34. An engagement pine 38 extends radiallyinwardly from the body 32 and engages the collar notch 28 when the guidepin 24 is received within the channel 34 and thereby forms an openingmeans for opening the valve member 23. As the cap 30 is rotated, theengagement pin 38 rotates the collar 20 to open the valve member 23.

FIG. 4 shows the interior structure of the cap 30 and discloses a firstaxial bore 40 extending into the body 32 from the first end 36 and sizedto receive the port body 18 (see FIG. 2). A second axial bore 42 extendssomewhat further into the cap body 32 and has a smaller diameter so asto receive the port collar 20 and cover plate 22. An annular groove 44in the body 32 at the first bore 40 receives an O-ring 46 to seal thecap 30 to the port 16.

An inlet valve bore 48 and an outlet valve bore 50 extend axially intothe valve body 32 in side-by-side relationship from a second end 52thereof. A header 54 extends from the second axial bore 42 to both ofthe inlet and outlet valve bores 48 and 50 to place them into fluidcommunication with the second axial bore 42. An inlet check valve 56 andan outlet check valve 58 are disposed respectively in the inlet andoutlet valve bores 48 and 50. Each of the inlet and outlet check valves56 and 58 allow only unidirectional flow, and only in response to apredetermined pressure gradient. Similar check valves are described inthe Winn U.S. Pat. No. 4,129,145 issued Dec. 12, 1978 and incorporatedherein by reference.

In general, each of the inlet and outlet check valves 56 and 58comprises a tubular valve body 60 having an interior annular valve seat62. A poppet 64 disposed within the valve body 60 comprises: a discoidalvalve member 66 downstream of the valve seat 62, a discoidal spring seat68 upstream of the valve seat 62, and a shaft 70 which passes throughthe valve seat 62 and connects the valve member 66 and spring seat 68. Aspring 72 extends between the valve seat 62 and the spring seat 68 tobias the valve member 66 against the valve seat 62 and thereby form apositive closure means. When pressure against the valve member 66overcomes the force of the spring, the valve member 66 lifts off of thevalve seat 62 to allow flow through the valve body 60.

The check valves 56 and 58 allow the pressure to equalize between theinterior of the endoscope 10 and the environment surrounding theendoscope sheath 14, while preventing free flow of gas into theendoscope 10. As used herein, the pressure is considered equalized whenthe pressure differential across the sheath 14 is below a predeterminedvalue such that the sheath is protected and including a prudent safetymargin. The springs 72 determine the pressure necessary to open thecheck valves 56 and 58. Preferably, the spring force should require apressure differential of 1.5 to 5 pounds per square inch to operate thecheck valves. A check valve with no biasing, such as a simple swingcheck valve, could substitute for either or both of the check valves 56and 58. However, the slight biasing force provided by the springs 72keeps the check valves 56 and 58 closed when the pressure is equalize tofurther prevent antimicrobial gas from entering the endoscope during thesterilization cycle.

The sterilzation cap 30 is particularly useful with vapor phase hydrogenperoxide sterilization, either alone or in connection with a plasmafield, such as disclosed in the Jacobs et al. U.S. Pat. No. 4,643,876issued Feb. 17, 1987 and incorporated herein by reference. To furtherensure that hydrogen peroxide from the sterilization cycle does notreach the inside of the endoscope 10, a filter media 74 may be providedin the inlet valve chamber 48 or more preferably in the header 54. Thefilter 74 preferably comprises a material capable of acting as acatalyst to decompose the hydrogen peroxide into harmless water andoxygen. Copper, silver, iron, platinum and their alloys are among themetals which act as a catalyst against hydrogen peroxide. Copper woolhas been found to be particularly suitable as a filter material.

Other means may be provided for preventing a residual anti-microbialagent from entering the endoscope 10, at least in a harmful form. Forhydrogen peroxide anti-microbials, other catalysts such as catalase orchemical reactants may be provided to decompose or otherwise renderharmless any residual hydrogen peroxide. Further, an absorbent, such ascellulosic material, may be provided in addition to or in place of thecopper filter 74 to absorb residual hydrogen peroxide and prevent itfrom entering the endoscope 10. Alternatively, a filtration membrane maybe provided for allowing the passage of air but blocking the passage ofhydrogen peroxide.

While these techniques are particularly useful for eliminating residualhydrogen peroxide, they also may eliminate residual amounts of otheranti-microbial agents used in similar sterilization cycles. Catalysts,reactive chemical agents, absorbents, physical filters such asfiltration membranes or other means may be used to prevent activeanti-microbial agent from entering the endoscope while allowing air topass into and out of the endoscope. For instance, in the case of anacidic or basic anti-microbial agent, an appropriate substance may beadded to neutralize the pH into a harmless range.

Typically, instruments are placed into a vapor transmissive, microbefiltering wrap or container (not shown) prior to sterilization. Onetypical device is disclosed in the Nichols U.S. Pat. No. 4,716,025issued Dec. 29, 1987 and incorporated herein by reference. After thesterilization procedure is complete, the instruments may be left insideof the wrap or container until ready for use, thus maintaining theirsterility. Often specialized containers are provided for instrumentssuch as endoscopes. To promote operator compliance in using the cap 30,it could be attached to such a specialized container whereby theoperator would be reminded to employ the cap 30 during sterilization bythe cap's presence in the container. FIG. 5 illustrates, in blockdiagram form, such a container 76 for containing the endoscope 10. Aconnecting member 78 leads between the container 76 and the cap 30 sothat the presence of the cap 30 will remind an operator to attach thecap to the endoscope port 16 prior to a sterilization procedure.

To sterilize the endoscope 10 in a low pressure gaseous antimicrobialatmosphere, the sterilization cap 30 is first placed onto the port 16 ofthe endoscope 10. The guide pin 24 enters the channel 34 on the cap 30to guide the movement of the cap 30 onto the port 16. The cap 30 isfirst pushed axially onto the port and then rotated one quarter turn. Asthe guide cap 30 is pushed axially onto the port 16, the engagement pin38 travels through the notch 26 in the cover plate 22 and enters thenotch 28 in the collar 20. As the cap 30 is rotated through one quarterturn, the collar 20 rotates to place the valve member 23 into the openposition, thereby placing the interior of the endoscope into fluidcommunication with the second axial bore 42 of the cap 30.

Typically, pressure is reduced during such a sterilization cycle priorto application of the antimicrobial agent. As the pressure is reduced,the outlet check valve 58 opens to allow air within the endoscope toescape and protect the integrity of the elastomeric sheath 14. As thepressure in the endoscope 10 equalizes with its surrounding atmosphere,the outlet check valve closes and seals the interior of the endoscopefrom the sterilizing atmosphere. When used with a hydrogen peroxideantimicrobial agent, the filter media 74 neutralizes any of the hydrogenperoxide which may happen to leak past the inlet or outlet check valves56 and 58.

At the end of the sterilization cycle, the antimicrobial agent isscavenged from the environment surrounding the endoscope 10. Typically,the sterilization occurs within a sealed chamber, and when performed inconnection with electromagnetic radiation to produce a plasma field, thehydrogen peroxide is converted to water and oxygen during thesterilization cycle. However, in the absence of a plasma field, thehydrogen peroxide is typically vented from the chamber. In any event, atsome point after the sterilization is complete, the pressure is raisedwithin the sterilization chamber (not shown). At a predeterminedpressure gradient, the inlet check valve 56 opens to allow air withinthe sterilization chamber to enter the endoscope. If there is residualhydrogen peroxide within the sterilization chamber, the filter media 74will neutralize it before it enters the port 16. After the sterilizationcycle is complete, the sterilization cap should be removed from theendoscope 10.

While the invention has been described with regard to a particularembodiment thereof, those skilled in the art will understand, of course,that the invention is not limited thereto since modifications can bemade by those skilled in the art, particularly in light of the foregoingteachings. Reasonable variation and modification are possible within theforegoing disclosure of the invention without the departing from thespirit of the invention. For instance, the cap 30 would be quite usefulwith only the outlet check valve 58 and without the inlet check valve56. Sufficient structure underlies the sheath 14 in most endoscopes suchthat low pressures within the endoscope 10 will not likely damage thesheath 14. Also, it should be understood that the present invention,including the chemical agent filtration aspects, is useful in protectinginstruments not only during hydrogen peroxide based sterilization butalso during sterilization with other agents, including peracetic acid,which may possibly harm the interior of an instrument such as anendoscope.

What is claimed is:
 1. A method for sterilizing an endoscope using agaseous sterilizing agent and equalizing the pressure within an interiorspace of an endoscope with a pressure in an environment about theendoscope, the method comprising the steps of:reducing the pressure inthe environment; when the pressure in the interior space differs fromthe pressure in the environment by more than a predetermined firstvalue, opening a port between the interior space and the environment toequalize the pressure therebetween; admitting the sterilizing agent tothe environment; when the pressure within the interior space isequalized with the pressure in the environment, blocking the port toinhibit flow of gas or other matter from the environment into theinterior space through the port thereby inhibiting passage of any of thesterilizing agent in the environment into the port; and filtering thefluid flow through the open port to allow air to pass through the portbut to deactivate the sterilizing agent and thereby inhibiting thesterilizing agent from passing through the port in an active form.
 2. Amethod according to claim 1 wherein the first value is in the range of1.5 to 5 pounds per square inch.
 3. A method according to claim 1wherein the filtering step comprises the step of chemically decomposingthe sterilizing agent.
 4. A method according to claim 3 wherein thesterilizing agent comprises an oxidizing agent.
 5. A method according toclaim 4 wherein the filtering step comprises the step of passing theoxidizing agent over a catalyst which decomposes the oxidizing agent. 6.A method according to claim 5 wherein the oxidizing agent compriseshydrogen peroxide, and the step of decomposing the oxidizing agentcomprises contacting the hydrogen peroxide with a catalyst whichdecomposes the hydrogen peroxide into water and oxygen.
 7. A methodaccording claim 6 wherein the step of decomposing the agent comprisespassing the agent over a filter comprising a material selected from thegroup consisting essentially of copper, silver, iron, platinum and theiralloys.
 8. A method according to claim 7 and further comprising the stepof forming the filter material into a wool.
 9. A method according toclaim 6 wherein the step of opening the port occurs when the pressure inthe environment exceeds the pressure in the interior space by thepredetermined first value.
 10. A method according to claim 6 wherein thestep of opening the port occurs when the pressure in the interior spaceexceeds the pressure in the environment by the predetermined firstvalue.
 11. A method according to claim 10 and further comprising thestep of, when the pressure in the environment exceeds the pressure inthe interior space by a predetermined second value, opening the port toallow gas within the environment to flow into the interior space.
 12. Amethod according to claim 11 wherein the first and second values areequal.
 13. A method according to claim 11 wherein the second valueexceeds the first value.
 14. A method according to claim 11 and furthercomprising the steps of:placing the endoscope into a sterilizationchamber; lowering the pressure within the sterilization chamber belowatmospheric pressure and introducing an antimicrobial gas into thesterilization chamber, scavenging the antimicrobial gas from thesterilization chamber; and raising the pressure within the sterilizationchamber back to atmospheric pressure.
 15. A method according to claim 14and further comprising the step of placing the endoscope within asealed, gas transmissive, microbe impervious container prior to the stepof introducing the antimicrobial gas into the sterilization chamber. 16.A method according claim 6 wherein the step of decomposing the agentcomprises passing the agent over a filter comprising copper.
 17. Amethod according to claim 1 wherein the first value is in the range of 0to 5 pounds per square inch.